How to hide backend URL/URI with Nginx reverse proxy

Question

Our company develops a new SaaS solution which will be used by resellers and their customers. For the customers of our resellers should the solution be branded like it is a software application from the reseller himself. This is completely implemented exept 1 thing, the URL.

I did a lot of research how to hide an URL/URI and a reverse proxy seems to be the best solution. I read something about different software applications which i can use to build a reverse proxy and Nginx seems to be perfect for this job.

I installed a fresh CentOS server and i installed Nginx on it. It was pretty easy (even for me as Linix noob). After some struggeling with the config file i found how to configure Nginx as reverse proxy.

Now when i browse to my proxy ip (f.e. 192.168.1.100/SaaS) i see the SaaS solution which has another ip. In the address bar i see the reverse proxy ip, exacly as wished!

After i click on a link or button in the SaaS solution the IP in the address bar changes into the real IP of the SaaS solution.

I read this, this, this and many more topics but i cant get it work.

My config "location" part looks like this atm:

location /SaaS {
        proxy_pass http://192.168.1.200/login/;
}

As soon as change it into this (the correct configuration i found on the internet in multiple articles)

location /SaaS {
        proxy_pass http://192.168.1.200/login;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        include /etc/nginx/proxy_params;
}

I got an error "The page you are looking for is not found." from Nginx. What do i wrong?

Answer 1

you need to either use a find/replace plugin or update every link in your SaaS app to use the nginx ip (dns would be highly recommend instead)

https://www.nginx.com/resources/wiki/modules/substitutions/

substitute the backend ip with the proxy ip, it's usually possible to rewrite the $host as you have, but it seems your links do not use the variable to set their url.

Example:

server {
    listen       80;
    listen  [::]:80;
    server_name  sub-test.jacobdevans.com;
    root         /var/www/html/test;
 location / {

            sub_filter 'abc-test.jacobdevans.com' 'sub-test.jacobdevans.com';
            sub_filter_once off;
        }

}

server {
    listen       80;
    listen  [::]:80;
    server_name  abc-test.jacobdevans.com;
    root         /var/www/html/test;

 location / {

            sub_filter '123-test.jacobdevans.com' 'abc-test.jacobdevans.com';
            sub_filter_once off;
        }

}

server {
    listen       80;
    listen  [::]:80;
    server_name  123-test.jacobdevans.com;
    root         /var/www/html/test;

 location / {

            sub_filter 'sub-test.jacobdevans.com' '123-test.jacobdevans.com';
            sub_filter_once off;

        }
}

http://sub-test.jacobdevans.com/